[greatquux]

I found someone's solution that actually does seem to work, even if it's hacky! https://learn.microsoft.com/en-us/answers/questions/1640434/... and https://gist.github.com/SelimBasyouni/efec48a197bfefb59d4ff7... basically create an EML file with X-Unsent: 1 and if you open in New Outlook it will show as a draft. This could basically replace what we're doing with MAPI.

[jonrobertson]

I finished testing that solution earlier and it is what we'll initially implement, until a better solution is available. Note for anyone testing, the C# project created a file with CR/LF line endings, and it does not open as a draft in classic Outlook ("Old Outlook"). Changing the file to end with LF only solved the issue and works with classic and New Outlook.